Multicasting is a scheme for one-to-many communications over a network, such as an Internet Protocol (IP) network. Multicast uses network infrastructure efficiently by requiring the source to send a packet only once, even if the packet is delivered to a plurality of receivers. Some nodes in the network can replicate the packet to reach multiple receivers when necessary. The multicast scheme scales to a larger receiver population without requiring prior knowledge of which or how many receivers are present in the network. Examples of multicast communications at the Open Systems Interconnection (OSI) Data Link Layer, include Ethernet multicast addressing, Asynchronous Transfer Mode (ATM) point-to-multipoint (P2MP) virtual circuits, and Infiniband multicast.
In some networks, multicast is the delivery of a message or information to a group of destinations at about the same time. The message can be delivered in a single transmission from the source by creating copies automatically in other network elements, such as routers, according to the topology of the network. Multicast is commonly implemented in IP networks, for example in IP applications of streaming media and Internet television. In IP multicast the implementation of the multicast concept occurs at the IP routing level, where routers create suitable distribution paths for datagrams that are sent to a multicast destination address. IP multicast is widely deployed in enterprises, commercial stock exchanges, and multimedia content delivery networks. One enterprise use of IP multicast is for IP Television (IPTV) applications.